1. Field of the Invention
The present invention relates to a screw-type jack mounted mainly on a vehicle such as an automobile, a truck, and so on and used when the vehicle is jacked up for repair and tire change.
2. Description of Related Art
Conventionally, a screw-type jack for high lifting of a mid-load vehicle, a well-known jack called a potbellied jack is used. The potbellied jack has a hollow housing disposed to stand on a base. A cylindrical ram guide and ram are combined in the housing in a telescope style. Two screw shafts are screwed to each other in an axial direction inside the housing to be extendable/contractible in a vertical direction. Such a potbellied jack is described, for example, in Japanese Patent Laid-open Hei 7-196290.
A ram nut attached to a lower end portion of the ram is screwed onto the upper one of the two screw shafts. A bevel gear is fixed to a lower end portion of a lower screw shaft. A drive gear is engaged with the bevel gear. The drive gear is rotated from the outside by an operation handle to extend/contract the ram guide and the ram, whereby a vehicle mounting table disposed on an upper end of the ram is lifted or lowered, depending on the direction of rotation.
The housing of this conventional jack for automobile is formed in such a manner that one portion of a steel pipe expanded to a substantially conical pipe shape using a press. A portion adjacent to the expanded portion in the substantially conic pipe shape is drawn in a rectangular pipe shape. Consequently, forming these shapes using a press is complicated, difficult, and requires a lot of time and labor. Moreover, a forced strength is given to the housing at the time of forming. This method of forming often results in unacceptable shape errors and cracks in the material, which require rejection. Such rejection results in low productivity.
Also, in the above-described conventional jack for automobile, a cylindrical shaft portion for fitting the drive gear therein is welded to a fitting hole disposed in a lower part of a side surface of the housing, and a lower end portion of the housing is welded to a base. This welding consumes a lot of time and labor, and thus increases the production cost. Besides the cost disadvantage, the possibility of insufficient strength resulting from poor welding remains a concern.
In the conventional jack for automobile, an outer circumferential surface of the housing is painted after assembly is finished, with the ram and the ram guide accommodated therein. This painting is complicated and requires a lot of time and labor. In addition, only the outer surface of the housing can be painted. The inside of the housing, other parts, and so on are left unpainted, and therefore, there exists concern about rust prevention.
Poor painting easily happens since grease coated on the bevel gear melts out due to the exposure of the jack to a high-temperature condition before or during painting.
The welding angle of the cylindrical shaft portion relative to the housing is not fixed. A shaft portion of the drive gear directly contacts an inner circumference of the cylindrical shaft portion. Consequently, the drive gear and the periphery of the cylindrical shaft portion in which the drive gear is disposed are given a forced strength to generate heat due to friction heat when the jack is repeatedly lifted and lowered in load tests of the jack. Therefore, there are problems that the life of peripheral parts is shortened, a handle operation requires increased labor, and so on.
The ram and the ram nut of the conventional jack for automobile are separate members fixed to each other by some means such as welding in order to lower production cost. However, since this welding work requires a lot of time and labor, elimination of this operation is considered as one item to be improved.
In order to use the conventional jack for automobile and put its components in their accommodated state, an operation handle having a long grip is used. But there exists a problem that a lot of time is required for lifting and lowering the ram and the ram guide by this operation handle. Therefore, it has been demanded that some method be devised which can lift the ram and the ram guide quickly in a short time to an intended height when they are used and which can also return the ram and the ram guide to their original positions in a short time when they are accommodated after being used.
It is an object of the present invention to provide a screw-type jack for automobile which can solve the various problems described above.
It is a further object of the invention to provide a screw-type jack housing that can be efficiently formed and assembled of a housing and in which streamlined production of the housing at low cost is achieved by eliminating complicated forming work and troublesome welding operations, for the housing, can realize easy and precise surface treatment such as rust prevention to lengthen life and enhance strength, and can realize smooth and easy operation by an operation handle.
It is another object of the present invention to provide a jack for automobile in which a method is devised for a fixing means of a ram and a ram nut to enable its production cost to be further lowered.
It is yet another object of the present invention to provide a jack for automobile in which a method is devised to increase the lifting/lowering speed of a ram when necessary.
In order to achieve the above-described objects, in a screw-type jack for automobile comprising: a base; a hollow and integrated housing provided to stand on this base; a ram mounted in the center portion inside this housing in an axial direction to be extendable/contractible in a vertical direction; and a drive mechanism mounted in the housing, for extending/contracting this ram in the vertical direction, and in which the housing includes a cylindrical shaft portion protrudingly disposed on a lower part of a side surface of the housing, and a drive gear is pivotally and rotatably supported in this cylindrical shaft portion, the present invention defines the housing as constituted of a plurality of housing pieces, namely, vertically divided portions of the housing, wherein the housing pieces are mechanically joined to each other to form the housing. This structure makes it possible to realize easy and uniform forming of the housing by eliminating complicated and difficult forming; furthermore, to realize efficient forming and assembly and streamlined production of the housing at low cost by eliminating troublesome and high-cost welding; and moreover, to enable easy and precise surface treatment such as painting and plating of the housing pieces and so on, thereby lengthening their life and enhancing their strength.
The present invention provides a jack in which the housing is divided in the vertical direction along the axis position of the cylindrical shaft portion, so that forming of the housing pieces is facilitated.
The present invention also provides two-divided portions of the cylindrical shaft portion integrally formed with the housing pieces, so that inefficiency of disposing the cylindrical shaft portion separately as in the conventional art is eliminated and streamlined production is realized.
The present invention provides a housing that is divided into two pieces in the vertical direction. A pair of these housing pieces are formed symmetrically, so that the structure thereof is simplified and the production thereof is facilitated.
The present invention also provides a jack in which each of the housing pieces includes joining pieces along edge portions of the housing piece to extend from these edge portions. When the housing pieces are mechanically joined with each other to form one housing, the joining pieces of the housing pieces are fixed with each other by a rivet, so that welding of the housing pieces is eliminated to realize cost reduction of the housing.
The present invention provides a jack in which the housing piece includes: joining pieces along edge portions of each of the housing portions extend from these edge portions. A connecting piece extends from one or both of the joining pieces. When the housing pieces are mechanically joined with each other to form the housing, the connecting piece is folded to overlappingly fix the joining pieces with each other. In this structure, the housing pieces are fixed to each other by one press work without requiring welding, to further reduce cost.
The present invention provides a jack in which the housing includes a leg piece protruding from a lower end portion of the housing. The leg piece is fixed to the base by a rivet to eliminate welding, so that cost reduction is also realized here.
The present invention also provides a jack in which a bush or a bearing layer is interposed between an inner circumferential surface of the two-divided portions of the cylindrical shaft portion and a shaft portion of the drive gear, so that the drive gear can be rotated smoothly, labor necessary for driving operation is reduced, and heat generation in the periphery of the cylindrical shaft portion is prevented.
In a screw-type jack for automobile comprising: a base; a hollow and integrated housing provided to stand on this base; a ram guide mounted in a center portion inside this housing in an axial direction to be extendable/contractible in a vertical direction; a ram mounted in the ram guide to be extendable/contractible; and a screw shaft for extending/contracting the ram guide and the ram in the vertical direction, and in which the housing includes a cylindrical shaft portion provided protrudingly on a lower part of a side surface of the housing, and a drive gear is pivotally and rotatably supported in this cylindrical shaft portion, the present invention a housing that is constituted of a plurality of housing pieces, namely, vertically divided portions of the housing and both side portions of these housing pieces are mechanically joined with each other to form the housing. This structure makes it possible to realize easy and uniform forming of the housing by eliminating complicated and difficult forming work; and furthermore, to realize efficient forming and assembly and streamlined production of the housing at low cost by eliminating troublesome and high-cost welding. Moreover, easy and precise surface treatment such as painting and plating of the housing pieces and so on is enabled, thereby lengthening their life and enhancing their strength.
The present invention provides a jack in which the ram is constituted of a cylindrical portion and a rum nut. A circumferential groove is formed around an outer circumference of an inserting portion of the ram nut which is to be inserted to the cylindrical portion. After the inserting portion is inserted into the cylindrical portion, an inner surface of the cylindrical portion is bulged out and fixed to the circumferential groove by caulking an outer circumferential portion of the cylindrical portion. Thereby, the ram nut is fixed to the cylindrical portion without welding to realize cost reduction.
The present invention provides a jack in which a quick moving lever is added in order to move a ram quickly in a vertical direction. The quick moving lever is caught in a handle joint of a drive gear and rotates a handle joint with a small rotation radius.
The present invention provides a jack in which a spacer ring is attached between a handle joint of an operation handle and an end portion of an outer surface of the cylindrical shaft portion. The handle joint is attached to the shaft portion of the drive gear to swing freely via a pin, so that backlash of the shaft portion in an axial direction is prevented and the handle joint is free to swing easily.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.